When solid state switching devices (SSSDs) (e.g., MOSFETs) are used instead of conventional electromechanical relays or circuit breakers for AC high power applications, excessive leakage current can occur when the device is in an OFF state, thereby creating a safety issue. As one example, in an aircraft secondary electrical power distribution system (SEPDS), maintenance personnel may come into contact with the open end at the output of an SSSD and get startled when replacing an aircraft load.
While the Solid State Relay is becoming an alternative to the conventional electromechanical relay in both low power and high power applications due to the advantages of light weight, lack of maintenance required, and small size, leakage current of the SSSD in an OFF state due to its junction capacitance can raise safety concerns in some high power applications. As implemented in aircraft applications, the Solid State Relay is used to control the electrical loads, such as lighting and entertainment devices. In a maintenance mode of such an implementation, the operator may be exposed to the conductor contact during the maintenance tasks, such as changing a bulb, at the time when the Solid State Relay is supposed to be OFF. In this case, if the leakage current exceeds a certain level, the operator's safety might be at risk.
Aspects of the present invention address these safety issues when SSSDs are used as relays and/or circuit breakers in electrical power distribution systems.